Genus: Cigar- or foot-shaped; a single macronucleus and 1 to several vesicular or compact microuclei (Kudo, 1966). Species: Oblong; 50-105 (80-90) μm long; a compact micronucleus; two contractile vacuoles; fresh water (Kudo, 1966). Similar in shape to P. bursaria but much more rounded at both ends; 70-90 μm long; two conctractile vacuoles; a single ovoid macronucleus with a single micronucleus; caudal cilia present (Carey, 1992). Generally believed P. trichium = P. putrinum (see below)

31 μm 63 μm 94 μm; x 640

Images of collecting locality: A drainage ditch near rice field, Hirado, Yachiyo City, Chiba Pref., Japan, March 2, 2008 by Y. Tsukii